1. Field of the Invention
This invention relates to a process and apparatus for central metering of a first portion of fuel to form a lean fuel/air mixture and timed port injection of a remaining enriched portion of the fuel forming a stratified charge within a cylinder or combustion chamber of an internal combustion engine. This invention also relates to only timed port injection of a gaseous fuel forming a stratified charge within a cylinder or combustion chamber of an internal combustion engine.
2. Description of the Prior Art
Injection of liquid fuels into a manifold, a combustion chamber or cylinder of an internal combustion engine is familiar in the art. Existing designs also use a pre-chamber for inducing stratified charge in gaseous fueled engines. Timed port injection of gaseous fuels without forming a stratified charge is also known in the art. Injection of air or exhaust gas into an intake manifold to preform a stratified charge is known in the art.
A draft copy of "SAE Technical Paper Series, 891652, Electronic Fuel Injection for Dual Fuel Diesel Methane" by N. J. Beck, W. P. Johnson, A. F. George, P. W. Petersen, B. Vanderlee and G. Klopp for Future Transportation Technology Conference held in Vancouver, B.C., Canada, on Aug. 7-10, 1989, discloses types of possible systems which might be employed to meter and burn gaseous fuels. One of the types of possible systems discussed in such paper includes the following aspects: dual fuel, diesel pilot, mechanical pump and governor, multipoint, lean burn, timed gas pulse port injection, stratified charge, unthrottled, turbocharged and aftercooled. Such technical paper also discusses future plans for expanding use of the basic dual fuel retrofit kit for an OM-352 diesel engine. The referenced technical paper states that future research efforts will relate to a technique for accomplishing very lean burn with accompanying reduction in nitrogen oxides. Thus, a need exists for a system that uses fast-timed pulse injection of gas to generate a stratified charge.
"Intake Valve Deposits: Engines, Fuels, and Additive Effects", R. C. Tupa and D. E. Koehler, Automotive Engineering, Volume 97, No. 1, January, 1989, discusses excessive build-up of intake valve deposits due to multiport, liquid fueled, lean-burn engine designs. Such technical paper states that significant losses in fuel economy, increased emission and reduction in peak power result from heavy intake valve deposits. The technical paper also states that build-up of intake valve deposits is common, particularly with fast-burn/lean-burn engines.
U.S. Pat. Nos. 4,104,989 and 4,135,481 disclose preforming a predetermined portion of a stratified charge composed of a fuel/air mixture diluted by exhaust gas, within an intake manifold when an intake valve for a cylinder is in a closed condition. A remaining portion of the stratified charge is subsequently introduced with the predetermined portion of the stratified charge when the intake valve is opened, during the intake stroke of the engine. The '481 patent discloses diluting the predetermined portion of the stratified charge within the intake manifold with a pocket or curtain of recirculated exhaust gas. Both patents teach use of an additional air source or plural air sources to precharge a fuel/air mixture in a portion of the intake manifold, uniquely associated with a closed intake valve, with a structured fuel/air ratio layer. A predetermined quantity of pre-stratifying air is introduced into a portion of the intake manifold which is adjacent the intake valve. A replaceable orifice passage having a predetermined size is selected to "tune" the intake manifold portion. An air throttle valve is used to control the amount of air introduced into the intake manifold to control total mixture flow and power. When the intake valve is opened, the resultant pre-stratified air or lean mixture is initially introduced into the cylinder. The space adjacent the spark plug is filled with a fuel/air mixture supplied by a carburetor. Upon opening the intake valve, the initial quantity of air is drawn into the cylinder during the intake stroke to form a layer of air adjacent the piston. The '989 patent further discloses that upon opening of the intake valve during the intake stroke, the stratified charge created with the aid of auxiliary air intake devices is delivered to the cylinder forming: (1) a relatively rich fuel/air mixture layer adjacent the face of the piston, (2) a middle relatively lean fuel/air mixture layer, and (3) another relatively rich fuel/air mixture adjacent the spark plug. During the compression stroke of the piston, the layered or stratified charge in the cylinder essentially maintains its stratified characteristics with reduced volume.
U.S. Pat. Nos. 4,413,593 and 4,453,502 disclose combustion control through prestratification wherein diluent gas is injected for knock control of high compression ratio or supercharged engines. Injecting the diluent gas allows the engine to operate on lower octane fuel than would be possible without the diluent charge. U.S. Pat. No. 4,105,009 discloses an anti-pollution head construction for an internal combustion engine. "Automotive Engine Alternatives", R. L. Evans, The University of British Columbia, Vancouver, B.C., Canada, Plenum Press, New York and London, 1987, discloses a stratified charge of gasoline with port injection.
U.S. Pat. No. 4,628,881 discloses a pressure controlled fuel injection system for internal combustion engines. Hydraulic control of metering of a fuel charge is accomplished by adjusting the peak injection pressure and minimum injection pressure of an accumulator type injector. The '881 patent discloses precisely timing when fuel injection is to occur by controlling the shutdown of a solenoid valve. The volume of an accumulator chamber and maximum and minimum pressures within the accumulator chamber are adjusted to control the quantity of fuel injected and to control the pressure at which the fuel is injected into the combustion chamber of the engine.
U.S. Pat. No. 4,610,236 discloses a fuel supply control for a dual induction type engine intake system. During an initial period of fuel injection through a secondary fuel injection valve, a portion of the fuel cannot be drawn into the combustion chamber immediately but may be deposited on a wall of a secondary intake passage to form a liquid film flow so that there is a possibility that a lean mixture is temporarily produced during such initial period.
U.S. Pat. No. 4,151,821 discloses an engine fuel supply system in which a fine stream of gasoline is sprayed through a nozzle against a hot inner surface of a bottom wall within an atomization chamber.
U.S. Pat. No. 3,140,701 discloses a fuel regulating intake valve. U.S. Pat. No. 3,068,086 discloses an equalizing system for gaseous fuel feed for internal combustion engines. The '086 patent teaches adjusting fuel/air mixtures by physically changing an internal diameter balance tube. U.S. Pat. No. 4,308,843 discloses a slow run apparatus for gaseous fueled internal combustion engines where gas flows under pressure from a primary section through a cover inlet and into an air cleaner assembly. U.S. Pat. No. 3,114,357 discloses a vaporizing device for liquid propane gas engines. U.S. Pat. No. 4,395,992 discloses a device for proportioning a gaseous fuel and air for combustion in an internal combustion engine.
U.S. Pat. Nos. 3,195,525 and 3,269,713 discloses governors for internal combustion engines, particularly speed governors and governors of the suction type. U.S. Pat. No. 4,610,267 discloses a fast-response solenoid valve.